Power supply for a top drive

ABSTRACT

A method and apparatus for supplying non-hydraulic power to a tool unit during well operation. A top drive supplies power to a power consumer of the tool unit with a non-hydraulic power supply: a mechanical power coupling from the top drive to the tool unit, a wireless power coupling from the top drive to the tool unit, a local power supply on the tool unit, and/or combinations thereof. The non-hydraulic power supply may be capable of supplying at least 2 kW for at least 10 s. The system may include a fixed gear coupled to the top drive, a slewing ring meshed to the fixed gear, and a revolving gear meshed with the slewing ring and coupled to the tool unit. The slewing ring is configured to transfer rotational force from the fixed gear to the revolving gear, and may be rotated by rotating a torque shaft or actuating the fixed gear.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of patent application Ser. No.15/004,503 filed on Jan. 22, 2016, which incorporated herein byreference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to apparatus andmethods for tool unit power supply during a well operation. Moreparticularly, the present disclosure relates to apparatus and method fornon-hydraulic power supply to a tool unit from a top drive.

Description of the Related Art

During a well operation, various tool units (e.g., drilling tool unit,casing tool unit, cementing tool unit, etc.) are used with a top drive.A top drive almost always provides a power supply to the tool units forcommunication, identification, sensing, measuring, or actuatingcomponents. Typically, a wellbore is first formed to accesshydrocarbon-bearing formations (e.g., crude oil and/or natural gas) bydrilling. Drilling is accomplished by utilizing a drill bit that ismounted on the end of a drill string. To drill to a predetermined depth,the drill string is connected to a top drive on a surface rig via adrilling tool unit and is rotated by the top drive. After drilling tothe predetermined depth, the drilling tool unit, drill string, and drillbit are disconnected from the top drive. A casing tool unit is thenattached to the top drive to lower a section of casing into thewellbore. An annulus is thus formed between the casing string and theformation. The casing string may then be hung from the wellhead. Thecasing tool unit may then be replaced by a cementing tool unit toconduct a cementing operation to fill the annulus with cement. Thecasing string is cemented into the wellbore by circulating cement intothe annulus defined between the outer wall of the casing and theborehole. The combination of cement and casing strengthens the wellboreand facilitates the isolation of certain areas of the formation behindthe casing for the production of hydrocarbons.

On some tool units, for example, the casing tool unit, hydraulic energyis typically coupled to the tool unit to provide power for operationalactivities. However, hydraulic components (such hydraulic power unit,hydraulic swivel, connectors, hoses, valves, actuators, and pressurecylinders) can cause downtimes due to maintenance and contamination dueto leaks.

Therefore, there is a need for apparatus and methods for non-hydraulicpower supply from the top drive to the tool units during a welloperation.

SUMMARY

One embodiment of the present disclosure generally provides a top drivesystem that includes a top drive, a tool unit having a power consumer,and a non-hydraulic power supply selected from at least one of amechanical power coupling from the top drive to the tool unit, awireless power coupling from the top drive to the tool unit, a localpower supply on the tool unit, and combinations thereof. The powerconsumer is configured to receive power from the non-hydraulic powersupply, and the non-hydraulic power supply is capable of supplying atleast 2 kW for at least 10 s.

One embodiment of the present disclosure generally provides a method ofoperating a tool unit coupled to a top drive that includes connecting anon-hydraulic power supply to a power consumer on the tool unit;powering the non-hydraulic power supply with the top drive; andsupplying power to the power consumer with the non-hydraulic powersupply. The power supplied is at least 2 kW for at least 10 s.

One embodiment of the present disclosure generally provides a top drivesystem that includes a tool unit, a top drive for rotating the toolunit, a fixed gear coupled to the top drive, a slewing ring meshed tothe fixed gear, and a revolving gear meshed with the slewing ring andcoupled to the tool unit. The slewing ring is configured to transferrotational force from the fixed gear to the revolving gear.

One embodiment of the present disclosure generally provides a methodthat includes rotating a torque shaft of a tool unit with one or moredrive motors on a top drive; actuating a fixed gear on the top drive;and rotating the slewing ring through at least one of the rotating thetorque shaft and the actuating the fixed gear. The tool unit is coupledto a revolving gear that is meshed with a slewing ring.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1 illustrates a drilling system in a drilling mode, according to anembodiment of the present disclosure.

FIG. 2A illustrates a top drive of the drilling system. FIG. 2Billustrates components of a combined multi-coupler in a cross-sectionalview of the top drive.

FIG. 3 illustrates the torque sub from FIG. 2B, the torque sub having awireless power coupling.

FIG. 4 illustrates a casing tool unit, according to an embodiment of thepresent disclosure.

FIG. 5 illustrates the drilling system in a casing mode.

FIG. 6 A,B,C illustrate slip actuation by a casing tool unit, accordingto an embodiment of the present disclosure.

FIG. 7 A,B,C,D,E illustrate a mechanical power coupling according to anembodiment of the present disclosure.

FIG. 8A,B illustrates a wireless power coupling according to anembodiment of the present disclosure.

FIG. 9A illustrates an example power cycle during slip actuation. FIG.9B illustrates a tool unit with a mechanical power coupling, a wirelesspower coupling, and a local power supply.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

The present disclosure generally relates to apparatus and methods ofsupplying power to a tool unit during a well operation. Moreparticularly, the present disclosure relates to apparatus and method ofsupplying non-hydraulic power to a tool unit from a top drive.

A benefit amongst many provided by this disclosure allows for readysupply of power to meet short-term, high-power load demands.

FIG. 1 illustrates a drilling system 1 in a drilling mode, according toan embodiment of the present disclosure. The drilling system 1 mayinclude a drilling rig 1 r, a fluid handling system 1 f, a pressurecontrol assembly (PCA) 1 p, and a drill string 2. The drilling rig 1 rmay include a derrick 3 d, a rig floor 3 f, a top drive 4, and a hoist5. The rig floor 3 f may have an opening through which the drill string2 extends downwardly into the PCA 1 p.

The drill string 2 may include a bottomhole assembly (BHA) and a pipestring 2 p. The pipe string 2 p may include joints of drill pipeconnected together, such as by threaded couplings. The BHA is connectedto the pipe string 2 p, such as by threaded couplings and a drill bit 2b. The drill bit 2 b may be rotated (e.g., rotation 6 r) by the topdrive 4 via the pipe string 2 p, and/or the BHA may further include adrilling motor (not shown) for rotating the drill bit. The BHA mayfurther include an instrumentation sub (not shown), such as ameasurement while drilling (MWD) and/or a logging while drilling (LWD)sub.

An upper end of the pipe string 2 p may be connected to the top drive 4.The top drive may be a modular top drive as provided in co-pending U.S.Patent Application 62/107,599. The top drive 4 may include a controlunit, a motor unit 4 m, a tool unit 200 (e.g., a drilling tool unit 200d, a casing tool unit 200 c (FIG. 4), a cementing tool unit, etc.), apipe handler 4 p, a backup wrench 4 w, a rail 4 r, and a coupling thatallows tool unit 200 to dock with the top drive 4, for example, combinedmulti-coupler (“CMC”) 4 y. The coupling may be a CMC as provided inco-pending U.S. Patent Applications Nos. 62/216,843 and 62/214,310,which are hereby incorporated by reference. Alternatively, the couplingmay be any suitable coupling commonly known or used in the industry. Thetop drive 4 may be assembled as part of the drilling rig 1 r byconnecting ends of the rail 4 r to the derrick 3 d such that a front ofthe rail is adjacent to a drill string opening in the rig floor 3 f.

Alternatively, the top drive 4 may include twin rails instead of themonorail. Alternatively, the lower end of the rail 4 r may be connectedto the rig floor 3 f instead of the derrick 3 d.

The PCA 1 p may include a blowout preventer (BOP) and a flow cross. Ahousing of the BOP and the flow cross may each be interconnected and/orconnected to a wellhead 7, such as by a flanged connection. The wellhead7 may be mounted on a casing string 8 which has been deployed into awellbore 9 drilled from a surface 10 s of the earth and cemented intothe wellbore 9. The casing string 8 may extend to a depth adjacent abottom of an upper formation 10 u. The upper formation 10 u may benon-productive and a lower formation 10 b may be a hydrocarbon-bearingreservoir.

Alternatively, the lower formation 10 b may be non-productive (e.g., adepleted zone), environmentally sensitive, such as an aquifer, orunstable. Alternatively, the wellbore 9 may be subsea having a wellheadlocated adjacent to the waterline and the drilling rig 1 r may be alocated on a platform adjacent the wellhead. Alternatively, the wellbore9 may be subsea having a wellhead located adjacent to the seafloor andthe drilling rig 1 r may be a located on an offshore drilling system.

During drilling of the wellbore 9, once a top of the drill string 2reaches the rig floor 3 f, the drill string may be extended to continuedrilling. Drilling may be halted by stopping rotation 6 r of the motorunit 4 m and removing weight from the drill bit 2 b. A spider 52 maythen be installed into a rotary table 53, thereby longitudinallysupporting the drill string 2 from the rig floor 3 f. The tong actuatorof the backup wrench 4 w may be operated to engage the backup wrenchtong with a top coupling of the drill string 2.

As would be understood by one of ordinary skill in the art with thebenefit of this disclosure, each of the tool units 200 may have avariety of power consuming components. Such power consumers requirepower for certain activities during operations. Exemplary powerconsumers include a variety of sensors (e.g., rotation sensors, slipopen/set sensors, etc.), data collectors/communicators (e.g., counters,antenna, etc.), or other components (e.g., active identification devices222) that typically require a low level of power (e.g., about 2 W-about20 W). Certain activities conducted by exemplary power consumers mayrequire additional power (e.g., about 20 W-about 1 kW), for example, fora drilling tool unit 200 d to actuate an internal blowout preventer(IBOP), or for a cementing tool unit to actuate a launcher. Additionalpower may be stored by one or more energy buffers on tool unit 200(e.g., battery charging. Even higher power loads (e.g., about 1 kW-about20 kW) may be required for certain activities conducted by exemplarypower consumers, such as actuation of slips 57 s by casing tool unit 200c. For example, higher power loads may be required for between about 1 sand about 30 s. In some embodiments, the power load may be at leastabout 2 kW for at least about 10 s. The top drive 4 may supply power topower consumers of the tool units 200 through one or more of severalnon-hydraulic power supplies, including wireless power coupling (e.g.,inductive coupling), mechanical power coupling (e.g., drive axle), andlocal (on the tool unit) power supply (e.g., energy buffer). The topdrive 4 powers the non-hydraulic power supplies, which then supply powerto the power consumers. At times, power consumers on the tool units 200may be supplied power contemporaneously both from the local power supplyand from at least one of a mechanical power coupling and a wirelesspower coupling from the top drive. Appropriate selection and combinationof such systems can meet operational power needs that may vary by peakload demand, steady-state load demand, time of load, power levelcontrol, and time to reach peak.

FIG. 2A illustrates the top drive 4 coupled with tool unit 200. The topdrive 4 may include one or more (pair shown) drive motors 18, a becket19, a drive body 22, and a drive ring, such as torque drive gear 23 g.The drive body 22 may be rectangular, may have a thrust chamber formedtherein, and may have a central opening formed therethrough. The drivemotors 18 may be electric (shown) or hydraulic (not shown) and have arotor and a stator. A stator of each drive motor 18 may be connected tothe drive body 22, such as by fastening. The rotor of each drive motor18 may be torsionally connected to the torque drive gear 23 g forrotation (e.g., rotation 6 r in FIG. 1) thereof. Alternatively, topdrive 4 may instead have a direct drive unit having the drive motor 18centrally located.

FIG. 2B illustrates components of a CMC 4 y in a cross-sectional view ofthe top drive 4. The CMC 4 y may include a torque drive body 23 and atool dock 24. The torque drive body 23 may be cylindrical, may have abore therethrough, may have a flange 23 f formed in an upper endthereof, may have a bayonet profile 23 b formed adjacently below theflange 23 f, and may rotationally couple to the drive body 22 via one ormore bearings 27. The tool dock 24 may be configured to be coaxiallyinserted in, and latch to, torque drive body 23. For example, torquedrive body 23 may have a locking mechanism 23 k that can selectivelylock the tool dock 24 within the bore. Torque drive body 23 may share acentral axis 350 with tool dock 24. The tool dock 24 may be configuredto couple to a tool unit 200, thereby conveying torque from torque drivebody 23 to the tool unit 200. In some embodiments, the tool dock 24 isan integral structure of the tool unit 200. Attaching the tool dock 24to the CMC 4 y couples the top drive 4 to the tool unit 200, therebyallowing selective transfer of torque from the top drive 4 to the toolunit 200. In some embodiments, a torque sub 40 may be located on thetool dock 24, adjacent to a stationary portion of the drive body 22,such as the location illustrated in FIG. 2B.

In one embodiment, the tool unit 200 may be equipped with anidentification device 202, as shown in FIG. 2A. The identificationdevice 202 may be attached to an outer surface of the tool unit 200, forexample by adhesives. Alternatively, the identification device 202 maybe disposed in a recessed space for secure attachment. Alternatively,the identification device 202 may be embedded inside the tool unit 200when the identification device 202 does not require direct line of sightto interact with a corresponding identification reader, for example onCMC 4 y of top drive 4. Alternatively, identification device 202 may beintegrated to tool unit 200, for example by etching, carving, painting,printing, layer buildup, molding, etc. The identification device 202 maybe an identification device as provided in co-pending U.S. PatentApplication No. 62/203,712, which is hereby incorporated by reference.

The identification device 202 is disposed on the tool dock 24 of thetool unit 200 in FIG. 2A. Alternatively, the identification device 202may be disposed in any suitable locations on the tool unit 200. In anembodiment, the tool unit 200 may include two or more identificationdevices 202 positioned at various locations.

The identification device 202 may be a radio frequency identificationdevice (RFID), such as a RFID tag or a RFID chip. In an embodiment, theRFID includes preloaded information and data for automaticidentification. Preloaded information and data in the RFID may be readby a RFID reader nearby. The RFID may be read by a RFID reader withoutrequiring a direct line of sight.

In an embodiment, the identification device 202 may be a passive(non-powered) RFID that does not include or is not connected to anelectrical power source. The passive RFID may collect energy frominterrogating radio waves from a reader nearby and act as a passivetransponder to send preloaded information and data to the reader. Theidentification device 202 of FIG. 2A is a passive device without a powersource. Passive identification devices are easy to maintain and may beread anywhere.

As illustrated in FIG. 2B, the identification device may be an active(powered) identification device 222. In an embodiment, the activeidentification device 222 may include an energy buffer, such as abattery, a supercapacitor, or a pressure reservoir. Alternatively, theactive identification device 222 may include electrical circuits forreceiving external power. As shown in FIG. 2B, the tool unit 200 mayinclude one or more conductive pads 226 formed on an exterior surface oftool dock 24. Each conductive pad 226 may be connected to the activeidentification device 222 by a wire 224. The one or more conductive pads226 may be configured to form electrical connection with an externalpower supply, for example, a power output of the top drive 4. In anotherembodiment, a wireless power coupling (between the top drive 4 and thetool unit 200) may be used to power the active identification device222. In another embodiment, a mechanical power coupling (between the topdrive 4 and the tool unit 200) may be used to power the activeidentification device 222. Alternatively, the active identificationdevice 222 may include an internal power source. For example, the activeidentification device 222 may include an electric generator, such as ahydraulic generator that generates electrical power by hydraulics. Inanother embodiment, some of one or more conductive pads 226 may beadapted to connect with an interface of top drive 4 to transmit signalsbetween the active identification device 222 and the external unit. Forexample, some of one or more conductive pads 226 may be adapted toconnect with an interface on CMC 4 y of top drive 4.

In an embodiment, the one or more conductive pads 226 may be positionedon external surfaces of the tool dock 24 so that the activeidentification device 222 may be activated by the top drive 4 duringoperation. In one embodiment, the one or more conductive pads 226 andthe wire 224 may be electrically insulated from the tool dock 24.

In some embodiments, a torque sub may be provided on the tool unit 200such as on the tool dock 24. FIG. 3 illustrates an embodiment of atorque sub 40. The torque sub 40 may be generally located on a rotatableportion of the tool unit 200, such as the tool dock 24, adjacent to astationary portion of the drive body 22. As illustrated, the torqueshaft 35 is attached to the tool dock 24, and a non-rotating controlswivel 36 is positioned on the drive body 22, adjacent to the torqueshaft 35. The torque sub may include a recess 35 r of the torque shaft35, one or more load cells 41 a,t, one or more wireless couplings, suchas a wireless power coupling 42 and a wireless data coupling 43, a shaftelectronics package 44 r, a turns counter 45, a non-rotating interfacebox 47, and an interface electronics package 44 s. The interface box 47may be connected to a non-rotating outer barrel of the control swivel36, such as by fastening. The load cell 41 t may include a circuit ofone or more torsional strain gages and the load cell 41 a may include acircuit of one or more longitudinal strain gages, each strain gageattached to the recess of the torque shaft 35, such as by adhesive.

Each wireless coupling 42, 43 may include a shaft member 42 r, 43 rconnected to the torque shaft 35 and an interface member 42 s, 43 shoused in an encapsulation on the interface box 47. The wireless powercoupling members 42 r,s may each be inductive coils and the wirelessdata coupling members 43 r,s may each be antennas. The shaft electronicsmay be connected by leads, and the shaft electronics package 44 r, loadcells 41 a,t, and the wireless data coupling shaft member 43 r may beencapsulated into the recess.

Alternatively, an energy buffer may be disposed on tool unit 200 (forexample, local power supply 490 in FIG. 9B). The energy buffer may be abattery, a supercapacitor, or a pressure reservoir, and the wirelesspower coupling 42 may be omitted or used only to charge the energybuffer.

FIG. 4 illustrates an exemplary casing tool unit 200 c suitable forconnection to the CMC 4 y. The casing tool unit 200 c may include a tooldock 24, a clamp, such as a spear 57 for gripping the casing string 8(FIG. 5), one or more control lines 58, and a fill-up tool 59. The tooldock 24 may include a trunk 206 and a head 208. The tool dock 24 may beintegrated with the spear 57 or coupled to the spear 57 using aconnection such as a thread coupling. The spear 57 and fill-up tool 59may be connected together, such as by threaded couplings or otherwise totransfer torsional force.

The spear 57 of the casing tool unit 200 c may be capable of supportingweight of the casing string 8 (FIG. 5). As illustrated in FIG. 4, thespear 57 may include a linear actuator 57 a, a bumper 57 b, a collar 57c, a mandrel 57 m, a set of grippers, such as slips 57 s, a seal joint57 j, and a sleeve 57 v. The collar 57 c may be integrated with the tooldock 24, or alternatively threaded to the tool dock 24. The collar lowerthread may be engaged with an outer thread formed at an upper end of themandrel 57 m and the mandrel may have an outer flange formed adjacent tothe upper thread and engaged with a bottom of the collar 57 c, therebyconnecting the two members.

The seal joint 57 j may include an inner barrel, an outer barrel, and anut. The upper portion of the inner barrel is sealingly engaged with thelower end of the tool dock 24, and the lower portion is coupled to theupper portion of the outer barrel. The lower portion of the outer barrelmay be disposed in the recessed portion of the mandrel 57 m and trappedtherein by engagement of an outer thread of the nut. The outer barrelmay have a seal bore formed therethrough and a lower portion of theinner barrel may be disposed therein and carry a stab seal engagedtherewith.

The sleeve 57 v may have an outer shoulder formed in an upper endthereof trapped between upper and lower retainers. A washer may have aninner shoulder formed in a lower end thereof engaged with a bottom ofthe lower retainer. The washer may be connected to the lower flange,such as by fastening, thereby longitudinally connecting the sleeve 57 vto the linear actuator 57 a. The sleeve 57 v may also have one or more(pair shown) slots formed through a wall thereof at an upper portionthereof. The bumper 57 b may be connected to the mandrel 57 m, such asby one or more threaded fasteners, each fastener extending through ahole thereof, through a respective slot of the sleeve 57 v, and into arespective threaded socket formed in an outer surface of the mandrel,thereby also torsionally connecting the sleeve to the mandrel whileallowing limited longitudinal movement of the sleeve relative to themandrel to accommodate operation of the slips 57 s. A lower portion ofthe spear 57 may be stabbed into the casing joint 8 j until the bumper57 b engages a top of the casing joint. The bumper 57 b may cushionimpact with the top of the casing joint 8 j to avoid damage thereto.

As illustrated in FIG. 4, the sleeve 57 v may extend along the outersurface of the mandrel from the lower flange of the linear actuator 57 ato the slips 57 s. A lower end of the sleeve 57 v may be connected toupper portions of each of the slips 57 s, such as by a flanged (i.e.,T-flange and T-slot) connection. Each slip 57 s may be radially movablebetween an extended position and a retracted position by longitudinalmovement of the sleeve 57 v relative to the slips. A slip receptacle maybe formed in an outer surface of the mandrel 57 m for receiving theslips 57 s. The slip receptacle may include a pocket for each slip 57 s,each pocket receiving a lower portion of the respective slip. Themandrel 57 m may be connected to lower portions of the slips 57 s byreception thereof in the pockets. Each slip pocket may have one or more(three shown) inclined surfaces formed in the outer surface of themandrel 57 m for extension of the respective slip. A lower portion ofeach slip 57 s may have one or more (three shown) inclined innersurfaces corresponding to the inclined slip pocket surfaces.

Downward movement of the sleeve 57 v toward the slips 57 s may push theslips along the inclined surfaces, thereby wedging the slips toward theextended position. The lower portion of each slip 57 s may also have aguide profile, such as tabs, extending from sides thereof. Each slippocket may also have a mating guide profile, such as grooves, forretracting the slips 57 s when the sleeve 57 v moves upward away fromthe slips. Each slip 57 s may have teeth formed along an outer surfacethereof. The teeth may be made from a hard material, such as tool steel,ceramic, or cement for engaging and penetrating an inner surface of thecasing joint 8 j, thereby anchoring the spear 57 to the casing joint.

FIGS. 6A-6C illustrate an embodiment of casing tool unit 200 c poweredby one or more of a mechanical power coupling, a wireless powercoupling, or a local power supply. FIG. 6A illustrates the slips fullyretracted, e.g., disengaged with the casing string 8. As illustrated,the casing tool unit 200 c includes a drive gear 410 coupled to thespear 57 of the casing tool unit 200 c, though other configurations mayinclude drive gear 410 coupled to tool dock 24, for example on trunk206. In one embodiment, the drive gear 410 may be rotated by a localmotor powered by one or more of a mechanical power coupling from the topdrive, a wireless power coupling from the top drive, or a local powersupply. In another embodiment, the drive gear 410 may be rotated by amechanical power coupling from the top drive. The drive gear 410 isconfigured to transfer rotational force, thereby supplying power, todriven gear 310. In this embodiment, the drive gear 410 may rotate 310 rthe driven gear 310 by the use of one or more connectors 420. Exemplaryconnectors 420 may be a drive axle, a grooved sleeve, a set of gears,axles, and/or sleeves, or any other suitable connector that is capableof meshing with drive gear 410, meshing with driven gear 310, andtransferring rotational force from drive gear 410 to driven gear 310.Rotation 310 r of driven gear 310 about the central axis 350 of casingtool unit 200 c may exert a force on an actuation nut 320, for example,via internal threading (e.g., stub acme) of the driven gear 310 withexternal threading of the actuation nut 320. The internal surface of theactuation nut 320 is coupled to vertical guides 330 on the spearmandrel, which prevents the actuation nut 320 from rotating relative tothe spear mandrel. In this respect, rotation of the driven gear 310causes translation 320 a (e.g., lowering or raising) of the actuationnut 320 along the central axis 350. The actuation nut 320 is configuredto actuate the slips 57 s between an extended position and a retractedposition. In the illustrated embodiment, the actuation nut 320 iscoupled to the slips 57 s via a slot-pin mechanism 340. One end of thepin is coupled to the actuation nut 320, and the other end of the pin ismovable in a slot formed in the slips 57 s. Downward force by actuationnut 320 on slot-pin mechanism 340 pushes slips 57 s along the inclinedsurfaces of the mandrel, thereby wedging the slips 57 s toward theextended position.

In operation, the spear 57 may be inserted into a casing 8 with theslips 57 s in the retracted position, as shown in FIG. 6A. To extend theslips 57 s into engagement with the casing 8, the drive gear 410 isrotated by a local motor or a mechanical power coupling from the topdrive. Rotation of the drive gear 410 rotates the connector 420, whichin turn, rotates the driven gear 310. The drive gear 310 is rotatedrelative to the actuation nut 320, which causes downward translation ofthe actuation nut 320 along the vertical guides 330. The downward forceis transferred to the slips 57 s via the slot-pin mechanism 340, therebyurging the slips 57 s to move along the inclined surfaces of themandrel. In this manner, the slips 57 s are extended radially to engagethe casing 8. FIG. 6B illustrates the slips 57 s being extended by theactuation nut 320. FIG. 6C illustrates the slips 57 s in the extendedposition, e.g., engaged with the casing string 8 (FIG. 6A). In thisrespect, drive gear 410 acts as a power consumer when the casing toolunit 200 c actuates slips 57 s.

To disengage the slips 57 s, the direction of rotation 310 r of drivengear 310 is reversed. When the direction is reversed, the actuation nut320 is caused to move upwardly along the vertical guides 330. In turn,the slips 57 s are moved upwardly along the inclined surfaces of themandrel to retract the slips 57 s from the extended position. In thismanner, the slips 57 s are disengaged from the casing string 8 andreturned to the retracted position as shown in FIG. 6A.

Referring back to FIG. 4, the casing tool unit 200 c may include one ormore sensors (not shown), such as a position sensor for the linearactuator 57 a, and a position sensor for the bumper 57 b. Alternatively,the linear actuator 57 a may be electrically or pneumatically operatedinstead of hydraulically operated, and the control line 58 may be acontrol cable or pneumatic control line instead of a hydraulic controlline.

Alternatively, the clamp may be a torque head instead of the spear 57.The torque head may be similar to the spear 57 except for receiving anupper portion of the casing joint 8 j therein and having the grippersfor engaging an outer surface of the casing joint instead of the innersurface of the casing joint.

FIG. 5 illustrates the drilling system 1 in a casing mode. Injection ofthe drilling fluid into the casing joint 8 j and rotation thereof by thedrive motors 18 (FIG. 2A) may allow the casing joint 8 j to be reamedinto the wellbore 9 (FIG. 1). Once a top of the casing joint 8 j reachesthe rig floor 3 f (FIG. 1), another casing joint may be added tocontinue deployment. Deployment may be halted by stopping rotation ofthe motor unit 4 m. The spider 52 (FIG. 1) may then be installed intothe rotary table 53 (FIG. 1), thereby longitudinally supporting thecasing joint 8 j from the rig floor 3 f. The slips 57 s (FIG. 4) may bedisengaged, and a unit handler may be operated to deliver an additionaljoint of casing to the casing tool unit 200 c (FIG. 4). The top drive 4(FIG. 2A) may then be lowered to stab the additional casing joint intothe casing joint 8 j. The rotary table 53 may be locked, or a backuptong (not shown) may be engaged with the top of the casing joint 8 j,and the drive motors 18 may be operated to spin and tighten the threadedconnection between the casing joints 8 j, thereby forming the casingstring 8. The spider 52 may then be released and running of the casingstring 8 may continue.

When casing tool 200 c is in operation, as in FIG. 6, high power loadsmay be required to actuate the slips 57 s. In addition to bearing theweight of the casing string 8, actuating slips 57 s may requireovercoming friction between the interior surface of the slips 57 s andthe mandrel 57 m, which may be exceedingly high due to the weight of thecasing string 8 and/or the wedge shapes of the friction-bearingsurfaces. For example, power to disengage slips 57 s by rotation 310 rof driven gear 310 in FIG. 6B may be in the range of hundreds of wattsto tens of kilowatts for a few seconds. In some embodiments, theexpected power, load for actuating slips 57 s may be about 1 kW-about 20kW for from about 1 s up to about 60 s. The duration of the high powerload may vary from about 1 s, to several seconds, to up to about 5 s, orup to about 10 s, or up to about 30 s, or up to about 60 s or more. Insome embodiments, the expected power load may be in the range of about 5kW-about 15 kW, or about 8 kW-about 10 kW. In some embodiments, the highpower load may be at least about 2 kW, and the duration may be at leastabout 10 s. In normal operations, expected time between slip actuationmay be no less that about 1-3 minutes.

As illustrated in FIGS. 6A-6C, top drive 4 (FIG. 2A) may satisfy powerload requirements for slip actuation by supplying power using one ormore of a mechanical power coupling, wireless power coupling, or a localpower supply (e.g., local power supply 490 in FIG. 9B). As illustrated,drive gear 410 on an upper portion of casing tool unit 200 c transfersrotational force, thereby supplying power, to driven gear 310 on a lowerportion of casing tool unit 200 c. A motor on top drive 4 (e.g., servomotor 458 in FIG. 7B) may directly or indirectly actuate drive gear 410.In some embodiments, a local power supply (e.g., electric generator,hydraulic pump, energy buffer) on casing tool unit 200 c may supply someor all of the power required by drive gear 410. In such embodiments, thelocal power supply may act at times as a power consumer (e.g., whenstoring power in an energy buffer) and at other times as a source oflocal power.

In embodiments, a mechanical power coupling or a wireless power couplingfrom the top drive 4 may drive the local power supply 490 (FIG. 9B) oncasing tool unit 200 c, which may thereby provide rotation 310 r ofdriven gear 310 during actuation of slips 57 s. Additionally, themechanical power coupling, wireless power coupling, and/or such localpower supply may be connected to an energy buffer (such as a battery, asupercapacitor, or a pressure reservoir). In an embodiment, a mechanicalpower coupling and/or a wireless power coupling may work with one ormore of an local electric generator, a local hydraulic pump, a localpower supply, and an energy buffer on casing tool unit 200 c to meetoperational needs, for example by providing higher power, more stablepower, or to distribute power load amongst the systems. Any or all ofthe local electric generator, local hydraulic pump, local power supply,and energy buffer on casing tool unit 200 c may thereby act as powerconsumers.

FIG. 7A illustrates an example of a mechanical power coupling from thetop drive 4 to the tool unit 200. FIG. 7A is a schematic illustration ofthe fixed gear 450, slewing ring 460, and revolving gear 470, as seenfrom above tool unit 200. Revolving gear 470 is coupled to tool unit 200so that revolving gear 470 may rotate about its own axis and revolvearound the central axis 350 of tool unit 200. For example, revolvinggear 470 may be disposed on top of flange 23 f of torque drive body 23(FIG. 7C,D,E). In one embodiment, revolving gear 470 may be connected asinput to a power supply on tool unit 200, such as a local electricgenerator, a local hydraulic pump, or an energy buffer on tool unit 200.In another embodiment, revolving gear 470 may be directly coupled to atool unit application, such as drive gear 410 in FIG. 6. Fixed gear 450is coupled to top drive 4, possibly via drive body 22 of top drive 4. Inan embodiment, drive body 22 of top drive 4 includes a servo motor 458(FIG. 76) capable of actuating and driving fixed gear 450 at acontrollable, variable speed. Slewing ring 460 is configured to transferrotational force from fixed gear 450 to revolving gear 470. Slewing ring460 may rotate about central axis 350 without radial or axialtranslation. Slewing ring 460 may be supported on bearings or othermechanisms that reduce or eliminate friction between slewing ring 460and either top drive 4 or tool unit 200. For example, slewing ring 460may be connected with a low-friction coupling to CMC 4 y. Moreparticularly, slewing ring 460 may be connected with a low frictioncoupling to the top surface of flange 23 f of torque drive body 23.While slewing ring 460 does not rotate freely, since it meshes withfixed gear 450 and revolving gear 470, the rotation of slewing ring 460is not directly determined by the rotation of tool unit 200 relative totop drive 4. Although illustrated as having a larger radius than toolunit 200, slewing ring 460 may have a smaller, equal, or larger radiusas tool unit 200.

FIG. 7B illustrates an embodiment of a mechanical power coupling incontext of top drive 4. During operation, torque drive body 23 rotatesto provide torque to tool unit 200 and thereby to downhole tools, suchas drill string 2 (FIG. 1). Revolving gear 470, which is connected ontop of flange 23 f of torque drive body 23, revolves about central axis350. When fixed gear 450 is locked, for example when the servo motor 458on the drive body 22 halts rotation of fixed gear 450, meshing ofslewing ring 460 to fixed gear 450 halts rotation of slewing ring 460.Meshing of slewing ring 460 to revolving gear 470 thereby causes arotation of revolving gear 470 as it revolves about central axis 350.Likewise, when fixed gear 450 is actuated at a certain rotational speed,for example by a servo motor 458 on drive body 22, meshing of slewingring 460 to fixed gear 450 causes rotation of slewing ring 460 at arotational speed that can be determined from the rotational speed of thefixed gear 450 and the gear radii of fixed gear 450 and slewing ring460. Meshing of slewing ring 460 to revolving gear 470 thereby causes arotation of revolving gear 470 at a further determinable rotationalspeed as revolving gear 470 revolves about central axis 350.

In an embodiment, a top drive 4 rotates a tool unit 200 at a speed of250 rpm with a torque of 100.000 ft-lbf. A slewing ring 460 has a 2 ftdiameter. A fixed gear 450 has a 0.2 ft diameter, and a revolving gear470 also has a 0.2 ft diameter. When the tool unit 200 is stopped, thefixed gear 450 will rotate at 2.500 rpm. If the delivered power isassumed to be 1 kW, a torque of 1 kW/(2*Pi*250/60 s)=38.2 Nm=28.2 ft-lbfresults. If the tool unit 200 is rotated, the fixed gear 450 has tospeed up to 5.000 rpm or slow down to zero, depending on rotationaldirection.

FIG. 7C illustrates an embodiment of mechanical power coupling as seenfrom above top drive 4. FIG. 7D illustrates the same embodiment incross-section A-A of FIG. 7C. FIG. 7E illustrates the same embodiment incross-section B-B of FIG. 7C. In this embodiment, the mechanical powercoupling includes slewing ring 460 and one or more gears (e.g., transfergear 475), grooved sleeves, and axles (e.g., drive axle 480) acting withslewing ring 460 to supply power to tool unit 200. Slewing ring 460 isdisposed on the top surface of flange 23 f of torque drive body 23 witha low friction coupling (e.g., bearings 465). Drive axle 480 may bedisposed in a groove in tool dock 24 and/or tool unit 200. Revolvinggear 470 may provide rotational force to drive axle 480. Revolving gear470 may further power drive axle 480 to convey rotation to generatorgear 485. Generator gear 485 thereby powers local power supply 490(e.g., an electric generator, a hydraulic pump, or an energy buffer) ontool unit 200. Any or all of generator gear 485, local power supply 490,the electric generator, the hydraulic pump, and the energy buffer ontool unit 200 may thereby act as power consumers.

In an exemplary embodiment, fixed gear 450 may have a diameter ofbetween about 0.15 and about 0.25 ft, slewing ring 460 may have adiameter of between about 1.5 and about 2.5 ft, revolving gear 470 mayhave a diameter of between about 0.15 and about 0.25 ft, and drive axle480 may have a diameter of between about 0.05 and about 0.15 ft. Whenthe tool unit 200 is not rotating relative to top drive 4, fixed gear450 may turn counter-clockwise at a speed of about 2500 rpm. A servomotor 458 on drive body 22 may be used to actuate and maintain fixedgear 450's speed. The power might be 1 kW, so the torque supplied byfixed gear 450 is 28.2 ft-lbf. In reaction to the rotation of fixed gear450 (since the tool unit 200 is not turning), slewing ring 460 turnsclockwise with 250 rpm. The torque of 282 ft-lbf is applied, but thetorque drive body 23 is fixed by a brake. Revolving gear 470 therebyturns clockwise with 2500 rpm. Transfer gear 475 transfers power fromrevolving gear 470 to drive axle 480. Drive axle 480 turns with 5000 rpmand 14 ft-lbf. This example may occur during the casing job operations,especially during the activation of the slips.

In another embodiment, the top drive 4 may supply power to a tool unit200 via wireless power coupling. In one example, inductive coupling maybe used to supply power both for activities that require lower powerloads (e.g., about 2 W-about 20 W) and for activities requiringadditional power between about 20 W and about 1 kW.

As illustrated in FIG. 3, wireless power coupling 42 may include a shaftmember 42 r connected to the torque shaft 35 and an interface member 42s housed in an encapsulation on the interface box 47. The wireless powercoupling members 42 r,s may each be inductive coils. Even though thewireless power coupling 42 supplies power from the stationary interfacemember 42 s to the rotatable shaft member 42 r, the wireless powercoupling 42 is devoid of any mechanical contact between the interfacemember 42 s and the shaft member 42 r. In general, the wireless powercoupling 42 acts similar to a transformer in that it employselectromagnetic induction to transfer electrical energy from onecircuit, via a primary coil (e.g., component of interface member 42 s),to another, via a secondary coil (e.g., component of shaft member 42 r),and does so without direct connection between circuits (i.e., theprimary and secondary coils are structurally decoupled from each other).Other examples and applications of inductive couplings are described inU.S. Pat. No. 7,882,902, which is assigned to the same assignee as thepresent application and is herein incorporated by reference.

Inductive coupling benefits from having no moving parts, resulting inless system wear and greater reliability. However, standard inductivecoupling may suffer energy losses if the magnetic field protrudes intosurrounding metals, especially ferromagnetic materials. Standardinductive coupling may also suffer energy losses due to non-idealmagnetic coupling of the coils. Inductive energy losses may furtherimpede operations by heating surrounding metals, thereby creatinghazardous conditions, particularly when used near flammable materials.

In another embodiment, the wireless power coupling in conjunction with alocal energy buffer may be configured to supply higher power loaddemands (e.g., about 1 kW-about 20 kW). In one embodiment, the wirelesspower coupling may include: a) ferrite segments that guide the magneticfield to avoid losses in surrounding metal, and/or b) a resonantcoupling of the primary and secondary coil system. In some embodiments,the use of ferrite segments and/or resonant coupling may allow thewireless power coupling in conjunction with a local energy buffer tosupply at least about 2 kW for at least about 10 s.

An exemplary wireless power coupling is illustrated in FIG. 8A-8B.Torque shaft 35 of a tool unit 200 is connected to wireless powercoupling shaft member 442 r (secondary coil system), which includes aferrite segment 446 and one or more coils 448. Likewise, wireless powercoupling interface member 442 s (primary coil system) includes a ferritesegment 446 and one or more coils 448. FIG. 8A illustrates across-section through the center of torque shaft 35. In this embodiment,wireless power coupling shaft member 442 r and wireless power couplinginterface member 442 s encircle torque shaft 35. In other embodimentsthe wireless power coupling members may be one or more broken or partialrings, segments, or arcs to better serve operational needs. The coils448 will typically comprise about 1 to 4 turns of copper pipe. Theferrite segments 446 may be divided into pieces. Note that, unlike atypical power transformer, the wireless power coupling members 442 r,sdo not share a single ferrite segment 446. At times during operation,torque shaft 35 may rotate about its central axis 350, causing wirelesspower coupling shaft member 442 r to likewise rotate. At other timesduring operation, torque shaft 35 may not rotate. Wireless powercoupling interface member 442 s remain essentially fixed, being attacheddirectly or indirectly to the top drive 4 (FIG. 2A). A high frequency(e.g., between about 40 kHz and 60 kHz) generator 440 on the top drive 4may help to drive the primary coil in the wireless power interfacemember 442 s. Use of a high frequency generator 440, as illustrated inFIG. 8B, allows for power transfer through inductive coupling both whentorque shaft 35 is rotating and when it is still relative to top drive4. Ferrite segments 446 generate a magnetic field 446B between thewireless power coupling shaft member 442 r and the wireless powercoupling interface member 442 s. Magnetic field 446B acts to align themagnetic fields of the coils 448 in the wireless power coupling shaftmember 442 r with the magnetic fields of the coils 448 in the wirelesspower coupling interface member 442 s. In an embodiment, the fixation ofwireless power coupling interface member 442 s to top drive 4 allows fora minimal amount of movement as would be required to align the magneticfields of the coils 448. Alternatively or additionally, the connectionof wireless power coupling shaft member 442 r to torque shaft 35 mayalso allow for a minimal amount of movement as would be required toalign the magnetic fields of the coils 448. Such alignment may reduceenergy-damping induction into surrounding steel.

Even with alignment of the magnetic field, the coupling coefficient ofthe coils (the fraction of the flux of the primary that cuts thesecondary coil) will still be less than 1, decreasing the efficiency.For example, due to an air gap between the coils, the couplingcoefficient might be only 0.5, resulting in unacceptable power losses.This can be compensated by using resonant coupling techniques. Whenresonant coupling is used, each coil may be capacitively loaded so as toform a tuned LC circuit. If the primary and secondary coils are resonantat a common frequency, significant power may be transmitted between thecoils over a range of a few times the coil diameters at reasonableefficiency. Running the secondary at the same resonant frequency as theprimary ensures that the secondary has a low impedance at thetransmitter's frequency and that the energy is better absorbed. It isbelieved that power transmission from the primary coil (i.e., wirelesspower coupling interface member 442 s) to the secondary coil (i.e.,wireless power coupling shaft member 442 r) may be improved from about20% without resonant coupling to at least about 80% with resonantcoupling, and in some circumstances to as much as 95% with resonantcoupling.

In an embodiment, a wireless power coupling may drive a local powersupply, such as a local electric generator, a local hydraulic pump, anenergy buffer and/or another local power supply (e.g., local powersupply 490 in FIG. 9B) on tool unit 200. The wireless power couplingand/or such local power supply may be connected to an energy buffer(such as a battery, a supercapacitor, or a pressure reservoir). In anembodiment, the wireless power coupling may work with one or more of alocal electric generator, a local hydraulic pump, a local power supply,and an energy buffer on tool unit 200 to meet operational needs, forexample by providing higher power, more stable power, or to distributepower load amongst the systems. Any or all of the local electricgenerator, local hydraulic pump, local power supply, and energy bufferon tool unit 200 may thereby act as power consumers. As would beunderstood by one of ordinary skill in the art with the benefit of thisdisclosure, the location of wireless power coupling shaft member 442 ron tool unit 200 and the location of wireless power coupling interfacemember 442 s on top drive 4 may vary to meet operational needs. However,wireless power coupling shaft member 442 r should be located at or neara rotating surface, wireless power coupling interface member 442 sshould be located at or near a non-rotating surface, and the twowireless power coupling members 442 r,s should be separated by no morethan about 1 inch.

The top drive 4 may supply power to power consumers of the tool units200 through one or more non-hydraulic power supplies such as wirelesspower coupling, mechanical power coupling, and local power supply. Thetop drive 4 powers the non-hydraulic power supplies, which then supplypower to the power consumers. Power may be supplied to the powerconsumers contemporaneously both from the local power supply and from atleast one of the mechanical power coupling and the wireless powercoupling. Appropriate selection and combination of such systems can meetoperational power needs that may vary by peak load demand, steady-stateload demand, time of load, power level control, and time to reach peak.For example, energy buffers may be located on the tool unit 200 tosupply supplemental power to meet peak load or short time-to-peak powerrequirements. Suitable battery technology may include a Nanophosphate®AHP14 Lithium Ion Prismatic Cell, currently available from A123 Systems,LLC., but other lithium iron phosphate batteries may work as well.Suitable batteries would not have a thermal runaway effect, unlikestandard battery technology used in cellphones and notebooks.Nonetheless, batteries should be mounted in a flameproof housing withadequate charge control. The size and weight of the batteries along withthe flameproof housing may affect where the energy buffer may be locatedon the tool unit 200. For example, the batteries may weigh about 10-20lbs, while the flameproof housing may add another about 20-40 lbs. Thedistribution of energy buffers on the tool unit 200 should be balancedto permit rotation of the tool unit 200. The number and type ofbatteries should be selected to provide sufficient power to actuateslips 57 s several times between charging. In normal operations,expected time to fully charge the energy buffers may be no more thatabout 1-3 minutes.

FIG. 9A illustrates an example power cycle during slip actuation. Thepower load, buffered power flow (buffer charging is less than zero,buffer discharging is greater than zero), and buffered energy level isshown over time. Initially, the power load is low, with power consumerssuch as sensors online. The energy buffer charges during this period. At10 s, slip activation begins: power load increases and buffered powerflow switches from charging to discharging. From 10 s to 11 s, slips areactivating, with an initial activation load that must overcome frictionand move the slips until they get into contact with the pipe. From 11 sto 16 s, the power load increases as the slips are activated, loadingenergy between the slips and the casing. At 20 s, the slips are clamped,thereby capping the power demand. From 20 s to 21 s, the slips springtension is locked by a self-locking mechanism. The casing connection ismade up for the next 30 s, and the low power load allows the energybuffers to recharge. The slips are then released, requiring less powerthan for activating. The slips are in zero position from 53 s to 58 s.The operation continues with new pipe lifting below the casing toolunit.

FIG. 9B illustrates a top drive 4 capable of supplying power to powerconsumers of tool units 200 through one or more non-hydraulic powersupplies such as wireless power coupling, mechanical power coupling, andlocal power supply. The top drive 4 powers the non-hydraulic powersupplies, which then supply power to the power consumers. Asillustrated, the coupling of CMC 4 y of top drive 4 to tool unit 200allows drive motors 18 to selectively rotate torque drive body 23,thereby selectively rotating tool dock 24 and tool unit 200. Wirelesspower coupling shaft member 442 r rotate with tool unit 200, whilewireless power coupling interface member 442 s remain essentially fixedto top drive 4. Ferrite segments 446 act to align the magnetic fields ofthe coils 448 in the wireless power coupling shaft member 442 r with themagnetic fields of the coils 448 in the wireless power couplinginterface member 442 s. Power is supplied in the form of electricalenergy from wireless power coupling interface member 442 s to wirelesspower coupling shaft member 442 r via electromagnetic induction withoutdirect connection between circuits. A servo motor 458 on drive body 22causes controlled rotation of a fixed gear 450 which meshes with andcauses rotation of slewing ring 460. Meshing of slewing ring 460 withrevolving gear 470 supplies mechanical power to tool unit 200. Forexample, revolving gear 470 may drive a drive axle 480 and directlysupply power to components of tool unit 200, such as rotating drive gear410 to actuate slips 57 s (FIG. 6). Alternatively or additionally, driveaxle 480 may convey rotation to generator gear 485, thereby supplyingmechanical power to a local power supply 490 (e.g., an electricgenerator, a hydraulic pump, or an energy buffer) on tool unit 200. Thetop drive 4 may therefore supply power to the tool units 200 through oneor more of several systems, including wireless power coupling (e.g.,inductive coupling), mechanical power coupling (e.g., drive axle orother connector for gearing), and local (on the tool unit) power supply(e.g., energy buffer). Appropriate selection and combination of suchsystems can meet operational power needs that may vary by peak loaddemand, steady-state load demand, time of load, power level control, andtime to reach peak.

An embodiment discloses a method comprising: rotating a torque shaft ofa tool unit with one or more drive motors on a top drive, wherein thetool unit is coupled to a revolving gear that is meshed with a slewingring; actuating a fixed gear on the top drive; and rotating the slewingring through at least one of the rotating the torque shaft and theactuating the fixed gear.

In one or more of the embodiments described herein, the method includesdriving an electric generator on the tool unit with the revolving gear.

In one or more of the embodiments described herein, the method includesactuating slips with the revolving gear.

In one or more of the embodiments described herein, the method includesproviding power to a local power supply on the tool unit with therevolving gear.

In one or more of the embodiments described herein, the local powersupply is an energy buffer.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A top drive system comprising: a tool unit; a top drive for rotatingthe tool unit; a fixed gear coupled to the top drive; a slewing ringmeshed to the fixed gear; and a revolving gear meshed with the slewingring and coupled to the tool unit, wherein the slewing ring isconfigured to transfer rotational force from the fixed gear to therevolving gear.
 2. The system of claim 1, wherein a rotation of theslewing ring is not directly determined by a rotation of the tool unitrelative to the top drive.
 3. The system of claim 1, further comprisinga low-friction coupling between the slewing ring and a combinedmulti-coupler of the top drive.
 4. The system of claim 1, furthercomprising a servo motor on the top drive configured to actuate thefixed gear at a selected rotational speed.
 5. The system of claim 1,further comprising a power consumer coupled to the revolving gear,wherein the transfer of rotational force is capable of supplying atleast kW of power to the power consumer for at least 10 s.
 6. The systemof claim 1, further comprising a drive axle, wherein the revolving gearprovides rotational force to the drive axle.
 7. The system of claim 6,wherein the drive axle is meshed with a generator gear on the tool unit.8. The system of claim 6, wherein the drive axle is meshed with a drivegear on the tool unit, wherein the drive gear is meshed with anactuation nut configured to actuate slips in response to rotation of therevolving gear.
 9. The system of claim 8, further comprising a slot-pinmechanism coupling the slips to the actuation nut.
 10. The system ofclaim 1, further comprising a power consumer coupled to the revolvinggear.
 11. The system of claim 1, further comprising: a torque gearcoupled to the tool unit, wherein the top drive is configured totransfer rotational force to the torque gear to rotate the tool unit.12. A top drive system comprising: a top drive comprising: a body; adrive gear coupled to the body; and a first motor coupled to the bodyand configured to rotate the drive gear; a mechanical power couplingcoupled to the top drive, comprising: a second motor; a fixed gearconfigured to be driven by the second motor; a slewing ring meshed tothe fixed gear; and a revolving gear meshed with the slewing ring,wherein the slewing ring is configured to transfer rotational force fromthe fixed gear to the revolving gear.
 13. The top drive system of claim12, wherein the top drive further comprises a torque drive bodyrotatable within the body of the top drive, wherein the drive gear iscoupled to the torque drive body, and wherein the slewing ring andrevolving gear are coupled to the torque drive body.
 14. The top drivesystem of claim 13, wherein the slewing ring is coupled to the torquedrive body by a low-friction coupling.
 15. The top drive system of claim12, wherein the slewing ring is coupled to the drive gear.
 16. The topdrive system of claim 12, further comprising a drive axle, wherein therevolving gear provides rotational force to the drive axle.
 17. A methodof operating a mechanical power coupling between a top drive and a toolunit coupled to the top drive, comprising: rotating a fixed gear coupledto the top drive; rotating a slewing ring meshed to the fixed gear inresponse to the rotation of the fixed gear; rotating a revolving gearmeshed to the slewing ring in response to the rotation of the slewingring; and rotating a drive axle of the tool unit in response to therotation of the revolving gear.
 18. The method of claim 17, furthercomprising rotating a generator gear in response to the rotation of thedrive axle to provide power to at least one of an electric generator, ahydraulic pump, and an energy buffer.
 19. The method of claim 17,further comprising actuating a plurality of slips of the tool unit inresponse to the rotation of the drive axle.
 20. The method of claim 17,further comprising rotating the tool unit with the top drive.